Image forming apparatus and controlling method thereof

ABSTRACT

An image forming apparatus includes an engine unit to execute an image forming job, a determination unit to repeatedly determine whether the image forming apparatus is in a standby state or not, based on whether the standby state to wait for execution of the image forming job is maintained for a predetermined time or not, and a controller to control the image forming apparatus to operate in a first power saving mode if it is determined that the image forming apparatus is in the standby state, wherein, in the first power saving mode, information stored in a volatile memory is copied to an internal memory and operation frequencies of a CPU, the volatile memory, and an intellectual property are lowered. Accordingly, power consumption in the standby state is reduced in a stepwise manner.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.12/659,731, filed Mar. 18, 2010, which claims the benefit of KoreanPatent Application No. 10-2009-84312, filed on Sep. 8, 2009, in theKorean Intellectual Property Office, the disclosures of which isincorporated herein by reference.

BACKGROUND

1. Field

Aspects relate to an image forming apparatus and a controlling methodthereof, and more particularly, to an image forming apparatus which iscapable of reducing power consumption in a standby state and acontrolling method thereof.

2. Description of the Related Art

An image forming apparatus refers to an apparatus which generates,prints, receives, and transmits image data, and includes a printer, ascanner, a copier, a facsimile machine and a multifunction peripheral(MFP) incorporating the functions of the aforementioned devices into asingle device.

Recently, an attempt to reduce power consumption in a normal operationstate in which the image forming apparatus normally operates is madealong with an attempt to reduce power consumption in a standby state inwhich the image forming apparatus does not perform a specific operation,that is, to reduce standby power.

The standby power refers to power which is always consumed regardless ofthe normal operation of the image forming apparatus. Currently, there isa movement to limit such standby power within a specific range as apolicy and reducing the standby power is of importance to the extentthat a product requiring high standby power will be prohibited frombeing manufactured in the future.

Therefore, there is a necessity to reduce standby power during a processin which a normal operation state is converted into a standby state orvice versa.

SUMMARY

Aspects provide an image forming apparatus which determines whether itis in a standby state or not and enters standby modes of different powerconsumption levels in a stepwise manner according to a result ofdetermination, and a controlling method thereof.

According to an aspect, there is provided an image forming apparatusincluding: an engine unit to execute an image forming job, adetermination unit to determine whether the image forming apparatus isin a standby state or not, based on whether the standby state to waitfor execution of the image forming job is maintained for a predeterminedtime or not, and a controller to control the image forming apparatus tooperate in a first power saving mode if it is determined that the imageforming apparatus is in the standby state, wherein, in the first powersaving mode, information stored in a volatile memory is copied to aninternal memory and operation frequencies of a CPU, the volatile memory,and an intellectual property are lowered.

The determination unit may repeatedly determine whether the imageforming apparatus is in the standby state or not.

According to the repetitive determination, if it is determined that thestandby state to wait for execution of the image forming job ismaintained for a predetermined time after the image forming apparatusoperates in the first power saving mode, the controller may control theimage forming apparatus to operate in a second power saving mode inwhich the CPU is set to use the information copied to the internalmemory and the volatile memory enters an idle mode.

According to the repetitive determination, if it is determined that thestandby state to wait for execution of the image forming job ismaintained for a predetermined time after the image forming apparatusoperates in the second power saving mode, the controller may control theimage forming apparatus to operate in a third power saving mode in whichpower supplied to the volatile memory and an operation module isinterrupted and the operation frequency of the CPU is lowered.

The image forming apparatus may further include a PLL unit to generateoperation frequency and provide the operation frequency to the CPU, thevolatile memory, and the intellectual property.

The internal memory may be a memory that stores information necessaryfor driving the intellectual property in a normal state in which theimage forming job is executed, and, in the first power saving mode,information stored in the volatile memory of the normal state may becopied to the internal memory.

The determination unit may determine whether an external signalrequesting the image forming apparatus to operate in a normal state toexecute the image forming job is input or not, and, if it is determinedthat the external signal indicates the normal state, the controller maychange the operation frequencies of the CPU and the volatile memory tonormal operation frequencies in response to the external signal.

The determination unit may determine whether an external signalrequesting the image forming apparatus to operate in a normal state toexecute the image forming job is input or not, and, if it is determinedthat the external signal indicates the normal state, the controller maychange the operation frequencies of the CPU and the volatile memory tonormal operation frequencies, and may set the volatile memory to be inan operation mode in response to the external signal.

The determination unit may determine whether an external signalrequesting the image forming apparatus to operate in a normal state toexecute the image forming job is input or not, and, if it is determinedthat the external signal indicates the normal state, the controller maychange the operation frequencies of the CPU and the volatile memory tonormal operation frequencies, supply power to the volatile memory andthe operation module, and copy information necessary for operating inthe normal state from the non-volatile memory to the volatile memory.

According to another aspect, there is provided a controlling method ofan image forming apparatus, including: determining whether the imageforming apparatus is in a standby state or not, based on whether thestandby state to wait for execution of an image forming job ismaintained for a predetermined time or not, and if it is determined thatthe image forming apparatus is in the standby state, entering a firstpower saving mode in which information stored in a volatile memory iscopied to an internal memory and operation frequencies of a CPU, thevolatile memory, and an intellectual property are lowered.

In the determining operation, it may be repeatedly determined whetherthe image forming apparatus is in the standby state or not.

According to the repetitive determination, if it is determined that thestandby state to wait for execution of the image forming job ismaintained for a predetermined time after the image forming apparatusoperates in the first power saving mode, the entering may includeentering a second power saving mode in which the CPU is set to use theinformation copied to the internal memory and the volatile memory entersan idle mode.

According to the repetitive determination, if it is determined that thestandby state to wait for execution of the image forming job ismaintained for a predetermined time after the image forming apparatusoperates in the second power saving mode, the entering may includeentering a third power saving mode in which power supplied to thevolatile memory and an operation module is interrupted and the operationfrequency of the CPU is lowered.

The internal memory may be a memory that stores information necessaryfor driving the intellectual property in a normal state in which theimage forming job is executed, and, in the first power saving mode,information stored in the volatile memory may be copied to the internalmemory.

The controlling method may further include: determining whether anexternal signal requesting the image forming apparatus to operate in anormal state to execute the image forming job is input or not, and, ifit is determined that the external signal indicates the normal state,changing the operation frequencies of the CPU and the volatile memory tonormal operation frequencies in response to the external signal.

The controlling method may further include: determining whether anexternal signal requesting the image forming apparatus to operate in anormal state to execute the image forming job is input or not, and, ifit is determined that the external signal indicates the normal state,changing the operation frequencies of the CPU and the volatile memory tonormal operation frequencies, and setting the volatile memory to be inan operation mode in response to the external signal.

The controlling method may further include: determining whether anexternal signal requesting the image forming apparatus to operate in anormal state to execute the image forming job is input or not, and, ifit is determined that the external signal indicates the normal state,changing the operation frequencies of the CPU and the volatile memory tonormal operation frequencies, supplying power to the volatile memory andthe operation module, and copying information from the non-volatilememory to the volatile memory.

Additional aspects and/or advantages will be set forth in part in thedescription which follows and, in part, will be apparent from thedescription, or may be learned by practice of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects and advantages of the invention will becomeapparent and more readily appreciated from the following description ofthe embodiments, taken in conjunction with the accompanying drawings ofwhich:

FIG. 1 is a block diagram illustrating an image forming apparatusaccording to an exemplary embodiment;

FIG. 2 is a view illustrating operation frequencies which are generatedby a phase-locked loop (PLL) unit and provided to each component;

FIG. 3 is a flowchart illustrating a controlling method of an imageforming apparatus according to an exemplary embodiment;

FIG. 4 is a flowchart illustrating the controlling method of FIG. 3 inmore detail;

FIG. 5 is a flowchart illustrating a controlling method of an imageforming apparatus according to another exemplary embodiment;

FIG. 6 is a flowchart illustrating a controlling method of an imageforming apparatus according to still another exemplary embodiment; and

FIG. 7 is a flowchart illustrating a controlling method of an imageforming apparatus according to still another exemplary embodiment.

DETAILED DESCRIPTION

Reference will now be made in detail to the present embodiments,examples of which are illustrated in the accompanying drawings, whereinlike reference numerals refer to the like elements throughout. Theembodiments are described below by referring to the figures.

FIG. 1 is a block diagram illustrating an image forming apparatusaccording to an exemplary embodiment. Referring to FIG. 1, an imageforming apparatus 100 includes an engine unit 110, a determination unit120, a controller 130, a CPU 140, a phase-locked loop (PLL) unit 150, anintellectual property 160, an internal memory 170, a volatile memory180, a non-volatile memory 185, and an operation module 190.

The determination unit 120, the controller 130, the CPU 140, the PLLunit 150, the internal memory 160, and the intellectual property 170constitute an application-specific integrated circuit (ASIC) unit 200 toperform their associated operations. The ASIC unit 200 may be realizedas a single chip such as an ASIC chip.

The engine unit 110 performs an image forming job such as printing,scanning, and copying.

The determination unit 120 determines whether the image formingapparatus 100 is in a standby state to wait for execution of an imageforming job or not. The standby state may include various power savingmodes according to power consumption levels. The determination unit 120may operate even in the standby state.

If an external signal is input, the determination unit 120 may determinewhether the image forming apparatus 100 is in a normal state (operationstate) or not.

The determination unit 120 may include a communication interface (notshown) and the external signal may be an interrupt signal which is inputfrom a host device (not shown) or a USB memory.

The determination unit 120 repeatedly determines whether the imageforming apparatus is in the standby state or not in order to enter thevarious power saving modes in a stepwise manner. For example, the imageforming apparatus 100 enters a first power saving mode, a second powersaving mode, and a third power saving mode in a stepwise manner. In thiscase, the power consumption can be further reduced in the second powersaving mode than in the first power saving mode and can be still furtherreduced in the third power saving mode than in the second power savingmode.

If it is determined that the image forming apparatus 100 is in thestandby state, the controller 130 controls the image forming apparatus100 to operate in the first power saving mode in which informationstored in the volatile memory 180 is copied to the internal memory 170and operation frequencies of the CPU 140, the volatile memory 180 andthe intellectual property 160 are lowered.

As a result of repetitive determination by the determination unit 120,if it is determined that the standby state to wait for execution of animage forming job is maintained for a predetermined time after the imageforming apparatus 100 operates in the first power saving mode, thecontroller 130 controls the image forming apparatus 100 to operate inthe second power saving mode in which the CPU 140 uses the informationcopied to the internal memory 170 and the volatile memory 180 enters anidle mode.

As a result of repetitive determination by the determination unit 120,if it is determined that the standby state is maintained for apredetermined time after the image forming apparatus 100 operates in thesecond power saving mode, the controller 130 controls the image formingapparatus 100 to operate in the third power saving mode in which thepower supplied to the volatile memory 180 and the operation module 190is interrupted and the operation frequency of the CPU 140 is lowered.

If the determination unit 120 determines that the external signalindicates a normal state when the image forming apparatus 100 is in thefirst power saving mode, the controller 130 changes the operationfrequencies of the CPU 140 and the volatile memory 180 to normaloperation frequencies.

If the determination unit 120 determines that the external signal is ina normal state when the image forming apparatus 100 is in the secondpower saving mode, the controller 130 changes the operation frequenciesof the CPU 140 and the volatile memory 180 to normal operationfrequencies, and changes the mode of the volatile memory 180 from theidle mode to an operation mode.

If the determination unit 120 determines that the external signal is ina normal state when the image forming apparatus 100 is in the thirdpower saving mode, the controller 130 changes the operation frequenciesof the CPU 140 and the volatile memory 180 to normal operationfrequencies, supplies power to the volatile memory 180 and the operationmodule 190, and copies information necessary for normal operation fromthe non-volatile memory 185 to the volatile memory 180.

The CPU 140 controls overall operation of the components of the ASICchip. The controller 130 controls the operation frequency of the CPU 140to be lowered in the first power saving mode and the third power savingmode. The operation frequency in the third power saving mode is lowerthan in the first power saving mode.

The PLL unit 150 generates various operation frequencies and providesthem to the components of the ASIC unit 200, such as the CPU 140, thevolatile memory 180, and the intellectual property 160.

The intellectual property 160, a functional device, performs variousfunctions, such as image processing to execute an image forming job inthe operation state and motor driving speed controlling. A plurality ofintellectual properties 160 may be provided according to the operationsto be performed.

The internal memory 170 is disposed in the ASIC unit 200. The internalmemory 170 may store information necessary for executing the function ofthe intellectual property 160 if the image forming apparatus 100 is inthe operation state to execute an image forming job. However, if theimage forming apparatus is in the standby state such as the first powersaving mode, the information which is stored in the volatile memory 180in the operation state is copied to and stored in the internal memory170.

Among the information stored in the volatile memory 180, minimuminformation such as information necessary for returning to the normaloperation state from the standby state may be copied to the internalmemory 170. Also, the information may be of diverse formats such ascode, program, and data, but should not be limited to these. Theinternal memory 170 may be realized as a static random access memory(SRAM).

The volatile memory 180 is disposed outside the ASIC unit 200 and theCPU 140 reads out information from the volatile memory 180 and performsoverall controlling operation in the operation state. In the secondpower saving mode, the volatile memory 180 enters a self-refresh mode,that is, an idle mode to perform refreshing by itself. Accordingly, thevolatile memory 180 is not required to receive a refresh command toperform refreshing at predetermined intervals from the controller 130.The volatile memory 180 may be realized as a dynamic random accessmemory (DRAM).

The non-volatile memory 185 is disposed outside the ASIC unit 200 andmay be realized as a read-only memory (ROM). In order to enter theoperation state by supplying power to the volatile memory 180 and theoperation module 190 which are turned off in the third power savingmode, the non-volatile memory 185 provides information which isnecessary for entering the operation state to the volatile memory 180.

The operation module 190 may be a printing module, a scanning module,and a copying module, and also may be a module to execute an imageforming job. Since the operation module 190 is not required to operatein the standby state such as the third power saving mode, the controller130 interrupts power supplied to the operation module 190.

FIG. 2 is a view illustrating the operation frequencies which aregenerated by the PLL unit and provided to each component. Referring toFIG. 2, various operation frequencies generated by the PLL unit 150 maybe applied to each component and each component operates according tothe operation frequencies. In the normal operation mode, more jobs canbe performed than in the first power saving mode and the second powersaving mode. For example, in the normal operation mode, the number ofoperations of reading and writing information with respect to a risingedge is higher than in the first power saving mode and the second powersaving mode. Likewise, more jobs are performed in the first and thesecond power saving modes than in the third power saving mode.

FIG. 3 is a flowchart illustrating a controlling method of an imageforming apparatus according to an exemplary embodiment. The controllingmethod of the image forming apparatus may be performed in the ASIC unit200 such as an ASIC chip. Referring to FIG. 3, the determination unit120 determines whether the standby state to wait for execution of animage forming job is maintained for a predetermined time or not (S310).Operation S310 is repeatedly performed.

If it is determined that the image forming apparatus 100 is in thestandby state, the image forming apparatus 100 enters the first powersaving mode in which information stored in the volatile memory 180 iscopied to the internal memory 170 and the operation frequencies of theCPU 140, the volatile memory 180, and the intellectual property 160 arelowered (S320). In operation S320, the operation mode in which the imageforming job is executed may be converted into the first power savingmode.

Accordingly, the controlling method of the image forming apparatusrepeatedly determines whether the image forming apparatus 100 is in thestandby state or not, and enters different power saving modes in astepwise manner according to the result of determination, so that powerconsumption can be reduced in the standby state.

FIG. 4 is a flowchart illustrating the controlling method of the imageforming apparatus of FIG. 3 in more detail. For convenience ofexplanation, it is assumed that the image forming apparatus 100 is in anoperation state (S410).

If the image forming apparatus 100 maintains the standby state for apredetermined time after having been in the operation state, thedetermination unit 120 determines whether a condition for entering thefirst power saving mode is satisfied or not (S420).

If the condition is satisfied (S420-Y), the image forming apparatus 100enters the first power saving mode (S430). In the first power savingmode, the information stored in the volatile memory 180 is copied to theinternal memory 170 and the operation frequencies of the CPU 140, thevolatile memory 180, and the intellectual property 160 are lowered underthe control of the controller 130.

Since the operation frequencies of the CPU 140, the volatile memory 180,and the intellectual property 160 are lowered to the minimum frequencythat can allow the volatile memory 180 to operate, power consumption ofeach component can be further reduced.

After entering the first power saving mode, if the image formingapparatus 100 maintains the standby state for a predetermined time, thedetermination unit 120 determines whether a condition for entering thesecond power saving mode is satisfied or not (S440).

If the condition is satisfied (S440-Y), the image forming apparatus 100operates in the second power saving mode (S450). In the second powersaving mode, the CPU 140 which has read out information from thevolatile memory 180 is set to use the information copied to the internalmemory 170, and the volatile memory 180 enters the idle mode, under thecontrol of the controller 130.

Accordingly, since the CPU 140 which has read out information from thevolatile memory 180 uses the minimum information copied to the internalmemory 170, power consumption can be further reduced. Also, if thevolatile memory 180 enters the idle mode, it is not necessary to receivea refresh command to perform refreshing at predetermined intervals fromthe controller 130 and thus power consumption can be further reduced.

After entering the second power saving mode, if the image formingapparatus 100 maintains the standby state for a predetermined time, thedetermination unit 130 determines whether a condition for entering thethird power saving mode is satisfied or not (S460).

If the condition is satisfied (S460-Y), the image forming apparatus 100operates in the third power saving mode (S470). In the third powersaving mode, the power supplied to the volatile memory 180 and theoperation module 190 is interrupted the operation frequency of the CPU140 is lowered, under the control of the controller 130.

Since the power supplied to the volatile memory 180 and the operationmodule 190 is interrupted, power consumption can be further reduced.Also, the operation frequency of the CPU 140 can be lowered to theminimum frequency that can allow the CPU 140 to operate. The minimumfrequency that can allow the CPU 140 to operate is lower than theminimum frequency that can allow the volatile memory 180 to operate inthe first power saving mode.

As described above, the image forming apparatus 100 enters the firstpower saving mode, the second power saving mode, and the third powersaving mode, which have different power consumption levels, in astepwise manner, and optimizes the power consumption according to eachmode, so that the power consumption can be reduced in the standby modeof the image forming apparatus 100.

The predetermined time set in operations S420, S440, and S460 may bedifferent from or equal to one another.

Although the first power saving mode, the second power saving mode, andthe third power saving mode are performed in sequence according to thecontrolling method of the image forming apparatus of FIG. 4, this shouldnot be considered as limiting. That is, if only the level of saved powercan be adjusted in a stepwise manner, various embodiments can beapplied. For example, the image forming apparatus 100 may directly enterthe third power saving mode from the first power saving mode or mayenter the third power saving mode after performing the first powersaving mode and the second power saving mode simultaneously.

FIG. 5 is a flowchart illustrating a controlling method of an imageforming apparatus according to another exemplary embodiment.

Referring to FIG. 5, the determination unit 120 repeatedly determineswhether a standby state to wait for execution of an image forming job ismaintained for a predetermined time or not (S510).

The controller 130 controls the image forming apparatus 100 to enter thefirst power saving mode by adjusting a power-saving level in a stepwisemanner according to the result of repetitive determination (S520). Morespecifically, in operation S520, the normal state is converted into thestandby state of the first power saving mode in which the controller 130controls a code stored in the volatile memory 180 in the normal state tobe copied to the internal memory 170 and the operation frequency of eachcomponent to be lowered.

It is determined whether an external signal requesting the image formingapparatus 100 to operate in the normal state to perform an image formingjob is input or not (S530).

If it is determined that the external signal is input, the operationfrequencies of the CPU 140 and the volatile memory 180 are changed tonormal operation frequencies (S540).

FIG. 6 is a flowchart illustrating a controlling method of an imageforming apparatus according to still another exemplary embodiment.

Referring to FIG. 6, the determination unit 120 repeatedly determineswhether a standby state to wait for execution of an image forming job ismaintained for a predetermined time or not (S610).

The controller 130 controls the image forming apparatus to enter thesecond power saving mode by adjusting a power-saving level in a stepwisemanner according to the result of repetitive determination (S620). Morespecifically, in operation S620, after the normal state is convertedinto the first power saving mode, the first power saving mode isconverted into the second power saving mode in which the CPU 140 is setto use information copied to the internal memory 170 (program jump) andthe volatile memory 180 enters the self-refresh mode.

It is determined whether an external signal requesting the image formingapparatus 100 to operate in the normal state to perform an image formingjob is input or not (S630).

If it is determined that the external signal is input, the operationfrequencies of the CPU 140 and the volatile memory 180 are changed tonormal operation frequencies, and the volatile memory 180 operates inthe normal operation mode (S640).

FIG. 7 is a flowchart illustrating a controlling method of an imageforming apparatus according to still another exemplary embodiment.

Referring to FIG. 7, the determination unit 120 repeatedly determineswhether a standby state to wait for execution of an image forming job ismaintained for a predetermined time or not (S710).

The controller 130 controls the image forming apparatus to enter thethird power saving mode by adjusting a power-saving level in a stepwisemanner according to the result of repetitive determination (S720). Morespecifically, in operation S720, after the first power saving mode isconverted into the second power saving mode, the second power savingmode is converted into the third power saving mode in which the powersupplied to the volatile memory 180 and the operation module 190 isinterrupted and the operation frequency of the CPU 140 is lowered.

It is determined whether an external signal requesting the image formingapparatus to operate in the normal state to perform an image forming jobis input or not (S730).

If it is determined that the external signal is input, the operationfrequencies of the CPU 140 and the volatile memory 180 are changed tonormal operation frequencies, power is supplied to the volatile memory180 and the operation module 190, and information is copied from thenon-volatile memory 185 to the volatile memory 180 (S740). Theinformation copied to the volatile memory 180 in operation S740 may bedata or code which has been pre-stored in the non-volatile memory 185 toallow the image forming apparatus 100 to operate in the normal state.

The embodiments include a computer readable recording medium whichincludes a program for executing the controlling method of the imageforming apparatus described above. The computer readable recordingmedium includes all kinds of recording devices which store data readableby a computer system. Examples of the computer readable recording mediumare a ROM, a RAM, a CD-ROM, a magnetic tape, a floppy disk, and anoptical data storage device. Also, the computer readable recordingmedium may store or execute a code which is distributed over a computersystem connected to a network and is readable by a computer in adistributed manner.

Although a few embodiments of the present invention have been shown anddescribed, it would be appreciated by those skilled in the art thatchanges may be made in this embodiment without departing from theprinciples and spirit of the invention, the scope of which is defined inthe claims and their equivalents.

1-21. (canceled)
 22. An image forming apparatus comprising: an engineunit to execute an image forming job; a determination unit to determinewhether the image forming apparatus is in a standby state or not; and acontroller to control the image forming apparatus to operate in a firstpower saving mode if it is determined that the image forming apparatusis in the standby state, wherein, in the first power saving mode,operation frequencies of at least one of a central processing unit(CPU), the volatile memory, and an function unit are lowered.
 23. Theimage forming apparatus as claimed in claim 22, wherein thedetermination unit determines whether the image forming apparatus is inthe standby state or not, based on whether the standby state to wait forexecution of the image forming job is maintained for a predeterminedtime or not.
 24. The image forming apparatus as claimed in claim 22,wherein the determination unit repeatedly determines whether the imageforming apparatus is in the standby state or not.
 25. The image formingapparatus as claimed in claim 24, wherein, according to the repetitivedetermination, if it is determined that the standby state to wait forexecution of the image forming job is maintained for a predeterminedtime after the image forming apparatus operates in the first powersaving mode, the controller controls the image forming apparatus tooperate in a second power saving mode in which the CPU is set to use theinformation copied to the internal memory and the volatile memory entersan idle mode.
 26. The image forming apparatus as claimed in claim 25,wherein, according to the repetitive determination, if it is determinedthat the standby state to wait for execution of the image forming job ismaintained for a predetermined time after the image forming apparatusoperates in the second power saving mode, the controller controls theimage forming apparatus to operate in a third power saving mode in whichpower supplied to the volatile memory and an operation module isinterrupted and the operation frequency of the CPU is lowered.
 27. Theimage forming apparatus as claimed in claim 22, further comprising aphase-locked loop (PLL) unit to generate operation frequency and providethe operation frequency to the CPU, the volatile memory, and thefunction unit.
 28. The image forming apparatus as claimed in claim 22,wherein, in the first power saving mode, further information stored in avolatile memory is copied to an internal memory.
 29. The image formingapparatus as claimed in claim 28, wherein the internal memory is amemory that stores information necessary for driving the function unitin a normal state in which the image forming job is executed, and, inthe first power saving mode, information stored in the volatile memoryof the normal state is copied to the internal memory.
 30. The imageforming apparatus as claimed in claim 22, wherein the determination unitdetermines whether an external signal requesting the image formingapparatus to operate in a normal state to execute the image forming jobis input or not, wherein, if it is determined that the external signalindicates the normal state, the controller changes the operationfrequencies of the CPU and the volatile memory to normal operationfrequencies in response to the external signal.
 31. The image formingapparatus as claimed in claim 25, wherein the determination unitdetermines whether an external signal requesting the image formingapparatus to operate in a normal state to execute the image forming jobis input or not, wherein, if it is determined that the external signalindicates the normal state, the controller changes the operationfrequencies of the CPU and the volatile memory to normal operationfrequencies, and sets the volatile memory to be in an operation mode inresponse to the external signal.
 32. The image forming apparatus asclaimed in claim 26, wherein the determination unit determines whetheran external signal requesting the image forming apparatus to operate ina normal state to execute the image forming job is input or not,wherein, if it is determined that the external signal indicates thenormal state, the controller changes the operation frequencies of theCPU and the volatile memory to normal operation frequencies, suppliespower to the volatile memory and the operation module, and copiesinformation necessary for operating in the normal state from thenon-volatile memory to the volatile memory.
 33. A controlling method ofan image forming apparatus, the method comprising: determining whetherthe image forming apparatus is in a standby state or not; and if it isdetermined that the image forming apparatus is in the standby state,entering a first power saving mode in which operation frequencies of atleast one of a CPU, the volatile memory, and a function unit arelowered.
 34. The controlling method as claimed in claim 33, wherein inthe determining operation, it is determined whether the image formingapparatus is in the standby state or not, based on whether the standbystate to wait for execution of the image forming job is maintained for apredetermined time or not.
 35. The controlling method as claimed inclaim 33, wherein in the determining operation, it is repeatedlydetermined whether the image forming apparatus is in the standby stateor not.
 36. The controlling method as claimed in claim 35, wherein,according to the repetitive determination, if it is determined that thestandby state to wait for execution of the image forming job ismaintained for a predetermined time after the image forming apparatusoperates in the first power saving mode, the entering comprises enteringa second power saving mode in which the CPU is set to use theinformation copied to the internal memory and the volatile memory entersan idle mode.
 37. The controlling method as claimed in claim 36,wherein, according to the repetitive determination, if it is determinedthat the standby state to wait for execution of the image forming job ismaintained for a predetermined time after the image forming apparatusoperates in the second power saving mode, the entering comprisesentering a third power saving mode in which power supplied to thevolatile memory and an operation module is interrupted and the operationfrequency of the CPU is lowered.
 38. The controlling method as claimedin claim 33, wherein, in the first power saving mode, furtherinformation stored in a volatile memory is copied to an internal memory.39. The controlling method as claimed in claim 38, wherein the internalmemory is a memory that stores information necessary for driving thefunction unit in a normal state in which the image forming job isexecuted, and, in the first power saving mode, information stored in thevolatile memory is copied to the internal memory.
 40. The controllingmethod as claimed in claim 33, further comprising: determining whetheran external signal requesting the image forming apparatus to operate ina normal state to execute the image forming job is input or not; and ifit is determined that the external signal indicates the normal state,changing the operation frequencies of the CPU and the volatile memory tonormal operation frequencies in response to the external signal.
 41. Thecontrolling method as claimed in claim 36, further comprising:determining whether an external signal requesting the image formingapparatus to operate in a normal state to execute the image forming jobis input or not; and if it is determined that the external signalindicates the normal state, changing the operation frequencies of theCPU and the volatile memory to normal operation frequencies, and settingthe volatile memory to be in an operation mode in response to theexternal signal.
 42. The controlling method as claimed in claim 37,further comprising: determining whether an external signal requestingthe image forming apparatus to operate in a normal state to execute theimage forming job is input or not; and if it is determined that theexternal signal indicates the normal state, changing the operationfrequencies of the CPU and the volatile memory to normal operationfrequencies, supplying power to the volatile memory and the operationmodule, and copying information from the non-volatile memory to thevolatile memory.